The present invention relates to a semiconductor device; and, more particularly, to a semiconductor memory device incorporating therein a ruthenium (Ru) electrode for securing a large capacitance and a method for the manufacture thereof.
As is well known, a dynamic random access memory (DRAM) with at least one memory cell comprised of a transistor and a capacitor has a higher degree of integration mainly by down-sizing through micronization. However, there is still a demand for downsizing the area of the memory cell.
To meet the demand, therefore, there have been proposed several methods, such as a trench type or a stack type capacitor, which is arranged three-dimensionally in a memory device to reduce the cell area available to the capacitor. However, the process of manufacturing three-dimensionally arranged capacitor is a long and tedious one and consequently involves high manufacturing cost. Therefore, there is a strong demand for a new memory device that can reduce the cell area with securing a requisite volume of information without requiring complex manufacturing steps.
In attempt to meet the demand, DRAM device employs a high dielectric material as a capacitor thin film such as barium strontium titanate (BST) and tantalum oxide (Ta2O5). Meanwhile, ferroelectric random access memory (FeRAM) employs a ferroelectric material as a capacitor thin film such as strontium bithmuth tantalate (SBT) and lead zirconate titanate (PZT) in place of a conventional silicon oxide film or a silicon nitride film.
However, even if the high dielectric material is used as the capacitor thin film, it has still a problem that an increase of a capacitance has a limitation by using a conventional method for forming the stack or the trench capacitor structure.
It is, therefore, an object of the present invention to provide a semiconductor device incorporating therein a ruthenium (Ru) electrode provided with rugged surface, wherein the rugged side surfaces are achieved by a second deposition of the Ru using a thermal chemical vapor deposition (TCVD) technique.
It is another object of the present invention to provide a method for manufacturing a semiconductor device incorporating therein an Ru electrode provided with rugged side surface, wherein the rugged side surfaces are achieved by a second deposition of the Ru using a thermal chemical vapor deposition (TCVD) technique.
In accordance with one aspect of the present invention, there is provided a semiconductor device for use in a memory cell, comprising: an active matrix provided with a semiconductor substrate, transistors formed on the semiconductor substrate, an insulating layer formed over the transistors and the semiconductor substrate, and a contact hole electrically connected to the transistors; a first ruthenium (Ru) layer formed over the contact hole and upon the insulating layer; and a second Ru layer with a rugged surface formed on top of the first Ru layer.
In accordance with another aspect of the present invention, there is provided a method for manufacturing a semiconductor device for use in a memory cell, the method comprising the steps of: a) preparing an active matrix provided with a semiconductor substrate, transistors on the semiconductor substrate, a contact hole electrically connected to the transistors and an insulating layer formed over the transistors; b) forming a first Ru layer on the contact hole and upon the insulating layer; and c) forming a second Ru layer with a rugged surface on the first Ru layer.